This invention relates to a fluid pump, and is particularly, although not exclusively, useful for the self-priming pumping of liquids.
Gear pumps are known which entrain fluid into the mesh of two counter-rotating cogs and expel the fluid under pressure, but such gear pumps need fast rotation of the gears and require to be manufactured with close tolerances.
The present invention overcomes or mitigates these drawbacks of the gear pump. The present invention provides a fluid pump comprising an internally-toothed drive belt drivingly coupled to a correspondingly externally-toothed first pulley wheel and arranged over a belt guide, which preferably takes the form of a second pulley wheel, spaced from the perimeter of the first pulley wheel, a fluid-tight housing containing the drive belt and pulley wheel, and means for coupling the motion of the first pulley wheel and the drive belt to that of an external drive; the housing having a fluid inlet port communicating with a space between the pulley wheels and the belt guide, and a fluid outlet port closely adjacent the region at which the drive belt engages tangentially with the first pulley wheel with their respective teeth in partial engagement; whereby motion of the first pulley wheel causes fluid from the space between the pulley wheel and the belt guide to be drawn into the nip of the first pulley wheel and the drive belt and then to be expelled under pressure to the fluid outlet port.
The invention also provides,a pumping system comprising a main fluid pump and a pump according to the invention used as a primer for the main fluid pump.
The fluid pump of the invention has been found surprisingly to pump with great efficiency even at low rotational speeds; whilst the gap between the drive belt and the housing is important, there is still a reasonable degree of manufacturing tolerance allowed, and the fluid pump can be mass produced from plastics materials with great economy.
In order that the invention may be better understood, preferred embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings.